Simvastatin is a potent antihypercholesterolemic agent. It is marketed under the name ZOCOR® (Merck). Simvastatin, Mevastatin, Lovastatin and Pravastatin are hexahydronaphthalene derivatives used as inhibitors of the enzyme HMG-CoA reductase, the rate-controlling enzyme in the biosynthetic pathway for formation of cholesterol in the human body. After oral ingestion, simvastatin, which is an inactive lactone, is hydrolyzed to the corresponding β-hydroxyacid form. This is an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. This enzyme catalyzes the conversion of HMG-CoA to mevalonate, which is an early and rate-limiting step in the biosynthesis of cholesterol.
Mevastatin, Lovastatin and Pravastatin are natural fermentation products which possess a 2-methylbutyrate side chain at C-8 of their hexahydronaphthalene ring system. Simvastatin can be derived synthetically from a fermentation product of Aspergillus terreus. 
Compounds possessing a C-8 2,2-dimethylbutyrate side chain, including Simvastatin, can be better inhibitors of HMG-CoA reductase than their 2-methylbutyrate counterparts. Thus 2,2-dimethylbutyrate derivatives may have greater promise for the treatment of atherosclerosis, hyperlipemia, familial hypercholesterolemia and similar disorders. However, these derivatives, including Simvastatin, are not naturally occurring and have to be produced synthetically. As a result, the introduction on the market of the more potent HMG-CoA reductase inhibitor Simvastatin has prompted the need for efficient, high yielding processes for manufacturing it.